Carbonic anhydrase is involved in the acidification of various body water compartments. This application constitutes a proposal to generate data that either support or negate a hypothesis stating that this enzyme plays a central role in parathyroid hormone and vitamin D3 induced bone resorption. Skeletal carbonic anhydrase will be studied quantitatively and compared to enzyme derived from several tissues where carbonic anhydrase is known to serve a physiological function. The accessibility of acetazolamide to bone cell carbonic anhydrase will be determined using high resolution autoradiography and labeled acetazolamide. Studies will be conducted to ascertain whether or not parathyroid hormone induces the synthesis of or activates skeletal carbonic anhydrase. Additional experiments will determine whether acetazolamide acts as a specific antagonist of bone resorption or as a generalized bone cell poison.